COMMIT_EDITMSG is a file which VSCode opens when you do not provide commit message in the Source Control plugin box –
The COMMIT_EDITMSG file looks like this –
Here you can write your commit message at the top.
If you don’t want this file to open up, you can turn the setting off in VSCode from here –
Use Editor As Commit Input setting and the file will not open anymore. You can find this – Settings -> Extensions -> Git
You can also use command line
git.useEditorAsCommitInput to turn it off.